On balance, EWG researchers found that zinc and titanium-based formulations are among the safest, most effective sunscreens on the market based on available evidence.

In other words, not only are zinc oxide and titanium oxide nanoparticle-based sunscreens OK, but they are safer and more effective than many non nanotechnology-enabled sunscreens.

What makes this statement so startling is that EWG is not known for treating regulators and industry with kid gloves. This is how the organization describes it’s way of working:

Our research brings to light unsettling facts that you have a right to know. It shames and shakes up polluters and their lobbyists. It rattles politicians and shapes policy. It persuades bureaucracies to rethink science and strengthen regulation.

EWG is about as far as you can get from a bunch of industry lackeys. Yet here they are endorsing one of the more controversial products of nanotechnology…

For the past few years, the safety of using nanometer-scale particles in sunscreens has been hotly debated. As manufacturers have turned increasingly to nanoscale mineral UV-blocking agents in place of more conventional chemicals, speculative questions over whether the nanometer-scale particles of titanium dioxide or zinc oxide being used could penetrate through the skin and harm people have been asked. In the absence of conclusive safety-focused research, some groups have suggested that nanoparticle-based sunscreens should be avoided in favor of more conventional products, where there we have a clearer idea of the possible risks. In 2007, Friends of the Earth published “A consumer guide for avoiding nano-sunscreens,” kicking off with:

Sun worshippers beware. While slathering up with sunscreens to block dangerous ultra-violet (UV) rays you may be exposing yourself to a new danger. Sunscreen manufacturers are adding nanoparticles to sunscreens to make sun-blocking ingredients like titanium dioxide and zinc oxide rub on clear instead of white. These nanoparticles are being added without appropriate labeling or reliable safety information.

Even EWG admit that their researchers were skeptical about the use of nanoparticles in sunscreens, and thought the organization would end up advising against their use.

Over the past few years, there has been a growing body of published data addressing the effectiveness and safety of nanoparticle-containing sunscreens. EWG researchers ploughed through nearly 400 studies in their quest to assess what the upsides and downsides might be for consumers. Importantly, they also compared these data to what is known about conventional UV-blocking agents like octinoxate and oxybenzone.

The result is a comprehensive, robust analysis that wouldn’t be out of place in a peer reviewed scientific journal. The conclusions are highly relevant to consumers concerned over which sunscreens to use, companies paranoid over how they present their products, and governments wondering how to regulate nanotech-enabled sunscreens. The report states:

Our study shows that consumers who use sunscreens without zinc and titanium are likely exposed to more UV radiation and greater numbers of hazardous ingredients than consumers relying on zinc and titanium products for sun protection. We found that consumers using sunscreens without zinc and titanium would be exposed to an average of 20% more UVA radiation — with increased risks for UVA-induced skin damage, premature aging, wrinkling, and UV-induced immune system damage — than consumers using zinc- and titanium-based products. Sunscreens without zinc or titanium contain an average of 4 times as many high hazard ingredients known or strongly suspected to cause cancer or birth defects, to disrupt human reproduction or damage the growing brain of a child. They also contain more toxins on average in every major category of health harm considered: cancer (10% more), birth defects and reproductive harm (40% more), neurotoxins (20% more), endocrine system disruptors (70% more), and chemicals that can damage the immune system (70% more) (EWG 2007).

We also reviewed 16 peer-reviewed studies on skin absorption, nearly all showing no absorption of small-scale zinc and titanium sunscreen ingredients through healthy skin. In a 2007 assessment the European Union found no evidence of nano-scale particles absorbing through pig skin, healthy human skin, or the skin of patients suffering from skin disorders (NanoDerm 2007). Overall, we found few available studies on the absorption of nano-scale ingredients through damaged skin, but nearly all other sunscreen chemicals approved for use in the U.S. also lack these studies.

In contrast to zinc and titanium, the common sunscreens octinoxate and oxybenzone absorb into healthy skin — in large amounts according to some studies. These 2 sunscreens can cause allergic reactions, can lead to hormone-driven uterine damage, and can act like estrogen in the body, raising potential concerns for breast cancer.

On balance, EWG researchers found that zinc and titanium-based formulations are among the safest, most effective sunscreens on the market based on available evidence. The easy way out of the nano debate would be to steer people clear of zinc and titanium sunscreens with a call for more data. In the process such a position would implicitly recommend sunscreen ingredients that don’t work, that break down soon after they are applied, that offer only marginal UVA protection, or that absorb through the skin.

EWG acknowledge that more research is still needed, alongside effective oversight, to ensure that nanotech-enabled sunscreens are as safe as possible. But the key message is that the current balance of evidence supports their use as a safe and effective alternative to more conventional sunscreens.

I cannot emphasize enough how important this report is. The analysis is credible and the conclusions drawn are supported by the current state of the science. It should reduce consumer concerns over using nanoparticle-based sunscreens, and allow them to make informed decisions that will result in better UV protection. It should also encourage companies developing and selling nanoparticle-enabled sunscreens to stop obscuring the fact – either by avoiding any mention of nanoparticles, hiding behind silly euphamisms alike “micronized,” or coming up with elaborate explanations of why their product doesn’t actually contain any nanoparticles. These are good products using an effective technology, and companies shouldn’t be shy to let people know!

That said, there is still work to be done. There are gaps in our understanding of how titanium dioxide and zinc oxide nanoparticles behave on the skin and in the environment that it would be good to fill. Approaches to testing these materials need to be fully evaluated. And regulators need to clarify the rules concerning the safe use of these materials.

Given what still isn’t known, EWG cautioned against the use of nanoparticles in cosmetics at the moment, where they are not being used to protect the wearer’s health. But when it comes to protecting the skin the organization was clear – nanoparticle-based sunscreens.

End Notes

The full EWG report on “Nanotechnology & Sunscreens” can be read here.

This is part of a larger review of sunscreens, which is accessible here.

Something not covered in the EWG report is nanoparticle agglomeration. Some companies have claimed that, while the basic size of titanium dioxide and zinc oxide particles they use is in the range of 1 – 100 nm, they form much larger agglomerates in the products and should therefore not be considered “nanoparticles.” While this may be the case for some products, it isn’t universal, and there are still questions over whether large agglomerates could disaggregate when applied to the skin. However, given the EWG’s findings and conclusions, the question of agglomeration doesn’t seem to be that important from a consumer’s perspective.

One concern over the use of titanium dioxide and zinc oxide nanoparticles in sunscreens is that these materials are photoactive, and could become more harmful when exposed to sunlight. As the EWG report notes, most manufaturers treat the nanoparticles to supress their photoactivity. Howere, there is some evidence that products containing photoactive particles could still be entering the market. Whether this is important from a health perspective is unknown, although the indications are that it probably isn’t a significant concern when the particle-containing sunscreens are appolied to healthy skin.

Something I’m seeing between the lines (though it may not in fact be there) is an implicit cost/benefit tradeoff. For people who are especially sensitive to the sun,one consideration seems to be the better performance of the nanoparticle sunscreens versus their risks, on the one hand, and the nano-free formula of competing products versus what seems to be a lower level of protection. Am I getting that right?

There’s a definite risk-benefit trade-off going on here, which involves more than just efficacy. Despite the often-speculative uncertainties surrounding nanoparticle-based sunscreens, it looks like they are probably safer for some users than sunscreens that don’t use particles as the active ingredient. Conventional UV blockers are known to cause harm in some cases, while no evidence for harm exists as yet for nanoparticle-based UV blockers.

It’s still a trade-off – do you go for the more effective and possibly safer product, even though it uses a new technology that hasn’t been tested to destruction, or do you stick with the product you know – even though it might be more harmful and not work as well?

Ultimately, this comes down to consumer choice – which means that the better the information we have available to us, the better off we are (in principle)!

Andrew I agree! The problem of big gov and big business treating the general public as ignorant folks is getting real old to a lot of people. I, for one am fed up! Consumers are smart and do care about what is in their food. It’s just that how can everyone know what they are eating if no one will properly regulate and label?
Great article,
DebbieDangers Of Nanoparticles In Sunscreen

I more than a little concerned to see consumers’ sunscreen choice being presented as “chemicals vs nano”. Nanoparticle-based zinc oxide and titanium dioxide sunscreens are not the only alternative to chemical-based sunscreens. When Friends of the Earth Australia surveyed 68 Australian sunscreen manufacturers last year for our Safe Sunscreen Guide we found that several offered nano-free (nearly clear) zinc based formulations. Our communication with sunscreen manufacturers indicates that the availability of such products is increasing.

I am also concerned that the significant limitations to existing nanoparticle skin penetration studies are being trivialised. There is a reason that costly, long-term studies are still underway in the US, Australia and elsewhere, and that is because existing studies have failed to address a lot of important ‘real life’ variables. After all, researchers showed five years ago that skin flexing was sufficient to enable skin penetration of 1,000nm beryllium particles. It seems reasonable to suggest that skin penetration by nanoparticles 20-40nm in size used in sunscreens could occur when people are exercising. There is similarly no recognition of the fact that many sunscreens are used in moisturisers and face creams which may also contain substances that act as skin penetration enhancers.

Furthermore, I note that whereas everyone is talking about healthy adult skin, there is little recognition that pimples, shaving rash, sunburn, eczema or other skin conditions could leave sunscreen wearers more vulnerable to nanoparticle uptake. I have also yet to see any data that looks at nanoparticle penetration through baby skin.

Finally, I think there is more than “some evidence” that sunscreen products which contain photo-active nanoparticles are still entering the market. A study published last year by Australian researchers at BlueScope Steel found that the photo-catalytic properties of nanoparticle-containing sunscreens were dramatic. Where installation workers wearing nano-sunscreens had touched roofs they were installing, subsequent localised roof ageing was accelerated 100 times. These results were replicated in controlled laboratory conditions.

There are still some very good reasons that people may wish to make a precaution-based decision to avoid using nano-sunscreens. We should avoid giving the false impression that the choice available to consumers is ‘poorly understood nanoparticles’ vs ‘dangerous chemicals’.

I would be the last to say that the safety of nanoparticles in sunscreens is a closed case – it clearly isn’t – but I do feel that pragmatic decisions need to be made, and that the balance of evidence so far is in favor of their use.

Working through your comments:

First, thanks for flagging up last year’s Safe Sunscreen Guide. It is important that consumers are aware that there are non-nano sunscreens available with mineral-based active ingredients. At the same time, I am a little wary that manufacturers are playing the definition game – finding ways of claiming that their products don’t contain nanoparticles, either because they have aggregated together, or they are a tad larger than the semi-formal 100 nm cut-off. This worries me because it moves the debate from what is safe, to a debate over definitions of size.

I would disagree that current skin penetration tests are being trivialized – there has been considerable investment in research in this area over the past few years, and despite trying hard, researchers are struggling to find any evidence for significant penetration. At the same time, there are gaps in our knowledge – which is why research continues. I would argue based on the current data that there are no compelling reasons not to use nanoparticles in sunscreens, but that to be complacent would be dangerous. Sally Tinkle’s study with the dextran beads (she didn’t use beryllium particles, although the study was designed to test a beryllium sensitization route hypothesis) is one of the very few studies that has shown the possibility of large particles penetrating through the skin, and should be interpreted very cautiously. At the time it was published, this was a very important piece of work – it demonstrated qualitatively that some particles could possibly pass through skin under some conditions. The setup she used was somewhat artificial and may have led to experiment-specific artifacts (which is why one experimental study alone is never enough to prove a point). But her work indicated that the question of skin penetration was an important one. Since then though, other researchers have failed to observe comparable skin penetration.

I must stress again that this doesn’t mean there is not an issue here – it just means that there is diminishing evidence for there being an issue. Maybe the right tests haven’t been done. Maybe we’re missing something. This is why the research needs to continue. But there comes a point where deciding against a product which could be potentially beneficial on the grounds of unsubstantiated speculation becomes counterproductive.

Next, the damaged skin issue you raise is an important one. There has been relatively little work on nanoparticle penetration through compromised or delicate skin – cuts, sunburn, baby skin, and this is an area that especially needs more work. It is beginning – see the citations in the EWG report – and the indications so far are that the issues related to using nanoparticle-based sunscreens on damaged skin are unlikely to be significantly worse than using non-nano sunscreens on such skin. Yet again, I don’t think we can afford to be complacent.

This raises an important issue of what happens if nanoparticles do penetrate through the skin and enter the body? There is remarkably little information available here, so we are once again in the realms of science-informed speculation. We know that particles are most likely picked up by the lymphatic system where they accumulate in the lymph nodes. We know that particles like titanium dioxide are relatively insoluble, and so will hang around for some time unless the body has adequate ways of clearing them as nanoparticles. We know that zinc oxide nanoparticles are more soluble, and will probably dissolve over time. We know that titanium dioxide has a very low toxicity, although this does increase according to some measures as particle size decreases. And we know that what is important in causing harm is the amount of stuff that enters the body – not just whether it will enter or not.

Pulling all this together, it is hard to make the case for nanoparticles on the skin presenting a clear risk. Certainly on the basis of this I would not hesitate to use nanoparticle-based sunscreens. But I would expect government and industry to continue filling in the knowledge gaps – just in case there is a problem.

Finally, the issue of photo-active nanoparticles. This does concern me I must confess, and I wrote about the BlueScope study last year. There is no reason why nanoparticles in sunscreens should be photoactive – there are ways of suppressing this that most manufacturers use. Yet without clear regulatory guidance, it seems there is very little to stop manufacturers using photoactive nanoparticles – either inadvertently or intentionally (although the latter makes bad business sense, as the photoactivity also degrades the long-term effectiveness of the product).

Two questions seem important here: Are photoactive particles on the skin a serious concern, and how many (and which) products are likely to contain them? On the first point, photoactive particles produce free radicals in the presence of UV radiation – highly active chemicals that can cause a lot of damage. But to cause damage they need to have access to living cells – and ideally the genetic material inside the cells. Free radicals are a fact of life and our bodies have evolved to deal with them, so we do have some protection. Free radicals also have a reasonably short lifetime because of their reactivity, and so if they are generated at the surface of the skin they are not likely to get to places where they can cause harm. If photoactive nanoparticles could penetrate inside living cells that were also exposed to UV radiation, we might have more of a problem. But there is scant evidence for either this degree of cell penetration, or there being sufficient penetration of UV to living cells that would lead to the generation of significant quantities of free radicals.

That said – more research is needed still to make sure current choices of using nanoparticles in sunscreens are as reasonable as they seem.

At the end of the day, consumers do have a right to choose what they think is best for them. Where there is uncertainty – even if it is somewhat speculative – that can lead to hard choices. Which is why I would argue strongly for as much independent and unbiased information being as freely available as possible – and in a form that is understandable to anyone who needs it. If a sunscreen contains nanoparticles (either as primary particles or as aggregates), it should be clear. The benefits of this ingredient should also be clear when compared to alternatives. Likewise, the possible downsides – together with the weight of evidence supporting this information – should be clear, again compared to the alternatives.

What I don’t think is helpful is groups – industry, academics or others – deciding what is right for consumers without enabling them to make their own informed decisions. This is particularly important where deciding not to use a product could be as harmful potentially as deciding to use it – as I think is the case with sunscreens.

As someone who’s alternately in the highest and second-highest risk group for skin cancer (initially I was in highest risk group but then it was altered to include hair colour as well as skin and eye colour so I got ‘demoted’ or ‘promoted’), I know I have to use sunscreen. While I’ve never been a sun-worshipper (and have the lack of wrinkles to prove it), I also know that I need the fastest and most efficient delivery system in order to get the sunscreen on, which means a spray application that doesn’t need to be reapplied every 10 seconds.

My informed choice, based on what I’ve learned to date from both scientists and dermatologists, and weighing the risks of not using sunscreen against the certainty that I will develop skin cancer if I live long enough (unless I’m prepared to stay indoors for the rest of my life) would be to use a non-photoactive nanotech zinc-oxide based sunscreen. What are the chances that I’ll be able to find one based on labeling alone? As an independent thinker (some might say born contrary), I like to make up my own mind on matters relating to both my health and my eco-footprint.

I think ultimately most people want at least the opportunity to make an informed choice over products. Even if they don’t read the labels, evidence suggests they like the idea that they could read them if they wanted.

Reading back over my reply to Georgia, I realize I may have sounded harsher than intended on organizations taking decisions out of the hands of consumers. The reality of course is that it is exactly these organizations that are best positioned to help consumers make informed decisions, by providing relevant product information and the means to understand and interpret it.

Labeling is part of empowering consumers to make informed choices, but is complex. For instance, slapping a “nano inside” label on a bottle of sunscreen would tell you precisely nothing about the product – it could refer to a plethora of things, some of which are good for you, others of which you might be a little more leary of.

Adding the “nano” suffix to the list of active ingredients makes more sense – so it’s clear when the product contains nano-titanium dioxide or nano-zinc oxide. This is the route Europe will be taking later this year with cosmetics. The difficulty here is deciding what constitutes “nano.” Europe will be referring to particles with a size between roughly 1 – 100 nanometers, and agglomerates or aggregates of these particles (I don’t have the precise language to hand). This isn’t perfect, but it is a pragmatic solution which will be more informative than not.

What the EU definition doesn’t do though is deal with ingredients where the mean particle diameter is larger than 100 nm, but where there are a substantial number of nanometer-scale particles in the distribution. One way to handle this is to identify ingredients which are engineered to have particles in the nanometer size range, or where a substantial proportion of the particle size distribution lies below 100 nm.

Even with the nano prefix on ingredients labels there are problems. Manufacturers will claim it doesn’t mean anything to consumers. Otherws sill claim it doesn’t give enough information. One way around this that has been discussed is to have a public registry of products and ingredients – so you can go to the web and get detailed information on what is in your favorite sunscreen, and what the relative benefits and uncertainties surrounding each component (and their combination with other components) are. This would be a lot of work to establish, but it’s an intriguing way of informing consumers that want to make choices on the best possible information.

Of course, such a registry would have to be independent and trustworthy!

The bottom line though is that the more consumers can be helped to make informed choices for themselves, the better.

Here’s an example of the kind of choice I make: I am allergic to peanuts and have been my entire life, so I’m an avid label reader. Since my reaction to peanuts doesn’t include life-threatening symptoms, the informed choice I make on that front is to avoid things that actually contain peanuts or peanut oil but not to worry when it says something was made in a factory where peanuts were processed. And to keep some antihistamines on hand at all times just in case, in the same way I keep bandages (plasters to you) and hydrogen peroxide and rubbing alcohol on hand for the times I cut myself with my dull knives (or while cutting up my American Express card with scissors, sigh).

I think the registry is a great idea but I’d like to see both labels and the registry on the principle that effective communication is that which helps people get information in the way they prefer to receive it, odd though their preferences may seem to be to those who don’t share them.

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Andrew Maynard is…

A professor and scientist with an unhealthy interest in the dark side – policy, communication and all that. When not writing and talking about science and technology, he chairs the University of Michigan Environmental Health Sciences Department and directs the UM Risk Science Center. More...

2020 Science is…

A personal blog about science and technology in the 21st century. Written by Andrew Maynard it tackles some of the knottier questions raised by science and technology, such as “where is technology innovation taking us?”, “what is the role of science in society?” and “how can science and technology be developed responsibly?” More…